The present invention relates to a non-slip system consisting of screw connection elements or screw closure elements with cams or grooves on the face, and of a spanner, also provided with cams, for tightening and loosening them. Within the framework of this patent application, screw connection elements are understood as meaning screws and nuts. The term is specifically intended to include tension nuts for clamping tool shanks in a tool holding fixture of a machine tool by means of a collet chuck. Screw closure elements are understood as meaning screwed-on or screwed-in covers, screw lids and the like.
DE 299 07 998 U discloses a system in which the tension nut is provided with radial grooves of dovetailed cross-section on the face, in which a spanner with pins or cams, also of dovetailed cross-section, engages for tightening and loosening the tension nuts. The dovetail connection between spanner and tension nut is intended to prevent the spanner from accidentally slipping during the clamping process.
One disadvantage of the dovetailed cross-section of the grooves and cams is the high notch effect in the comers and the resultant risk of damaging the cams or even breaking them off the spanner or parts of the nut. A further disadvantage is that pieces of the operator's clothing can get caught on the sharp edges or the operator can be injured.